The invention relates to a method for making handover decisions in a radio communications network comprising radio base stations and mobile units.
In accordance with the method of the present invention, decisions will be made concerning whether, and when, the handover of a mobile unit from one base station to another base station unit will occur. It is important that such decisions are correct because a wrong decision can result in communication being interrupted. Furthermore, wrong decisions concerning handover could also have the result that other mobile units are deprived of the possibility to communicate.
Neural networks are generally described in U.S. Pat. Nos. 4,796,199, 4,918,617 and 4,983,962. These patents are concerned with the organisation of a proposed architectural structure and provide a good source of information in relation to neural networks. In the following text, this information concerning neural networks will be utilised in connection with mobile telephony.
In mobile radio systems, communication is established between a mobile unit and a fixed unit, i.e. a base station. In practice, a mobile unit makes contact with a base station which is the most suitable for the purpose of establishing effective communication. The selection of a base station can be preprogrammed in relation to the geographic position of the mobile unit with respect to the base stations. Another possibility is for measurement to be made at the terminal, or at the base station. The parameters which will be considered are, for example, signal strength, distance and so forth. When a mobile unit has to change base station, it will normally be done in accordance with one of the above-mentioned principles. In the case where a wrong decision is made in respect of such a change, i.e. handover from one base station to another base station, an inferior transmission channel will be obtained, or alternatively, the communication will be interrupted. Any lack of handover can result in other connections being broken due to interference. It is thus of great significance that decisions concerning handover are made with the correct assumptions.
It is an object of the present invention to provide a method for making handover decisions in a radio communication network at the correct time. To this end, an artificial neural network has been created. The artificial neural network represents a model of the real radio communication network.